Spectral domain optical coherence tomographs (SD-OCTs) image target regions by splitting the light of a relatively broad-band light source into a reference light and an image light, and interfering a returned image light from the target with a returned reference light from e.g. a reference mirror. This interfering or image light is then spectrally decomposed and the spectral components are projected or transmitted to sensors of a sensor array in a detector. The SD-OCTs image the target at a range of z-depths essentially simultaneously at a specific xy lateral location by Fourier transforming the spectral components of the interfering light, sensed by the individual sensors. More traditional OCT systems, e.g. of the time domain type, image the range of z-depths by performing a z-scanning, resulting in considerably slower processing speeds. When an SD-OCT is combined with an x, y, linear, or xy scanner, two or three dimensional images of an entire target region or volume can be formed with remarkably high speed and resolution.
However, the high performance speed and high resolution imaging of the SD-OCTs is typically achieved by a highly precise control over most parameters of their specifications, including the bandwidth of the light source, the resolution and light collection efficiency of the optics and the readout speed of their detector array.
One class of SD-OCTs utilizes high numeric aperture imaging spectrometers with diffraction limited performance to satisfy these requirements. These devices often use a linear array of sensors as the detector, as those can provide faster readout speeds than sensors arranged in two dimensional arrays, and still scan through a target volume with reasonable speed. A typical linear sensor array, suitable for resolving the spectrum of a customary broad-band light source with high precision, may contain over 1,000 or more pixels in a linear arrangement. Presently, a size of individual pixels or sensors falls in the range of 10×10 microns to 20×20 microns. The small size of these individual pixels, however, poses formidable challenges for the alignment of the image beam to realize the potential high resolution of the SD-OCTs.